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From: Arnd Bergmann <arnd@arndb.de>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Dave Chinner <david@fromorbit.com>,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	joseph@codesourcery.com, john.stultz@linaro.org,
	hch@infradead.org, tglx@linutronix.de, geert@linux-m68k.org,
	lftan@altera.com, linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com
Subject: Re: [RFC 11/32] xfs: convert to struct inode_time
Date: Mon, 02 Jun 2014 14:52:13 +0200	[thread overview]
Message-ID: <15496653.1vSv1RUCC0@wuerfel> (raw)
In-Reply-To: <20140602115737.GB14276@thunk.org>

On Monday 02 June 2014 07:57:37 Theodore Ts'o wrote:
> On Mon, Jun 02, 2014 at 12:56:42PM +0200, Arnd Bergmann wrote:
> > 
> > I think you misunderstood what I suggested: the intent is to avoid
> > seeing things break in 2038 by making them break much earlier. We have
> > a solution for ext2 file systems, it's called ext4, and we just need
> > to ensure that everybody knows they have to migrate eventually.
> > 
> > At some point before the mid 2030ies, you should no longer be able to
> > build a kernel that has support for ext2 or any other module that will
> > run into bugs later....
> 
> Even for ext4, it's not quite so simple as that.  You only have
> support for times post 2038 if you are using an inode size > 128
> bytes.  There are a very, very large number of machines which even
> today, are using 128 byte inodes with ext4 for performance reasons.
> 
> The vast majority of those machines which I know of can probably move
> to 256 byte inodes relatively easily, since hard drive replacement
> cycles are order 5-6 years tops, so I'm not that concerned, but it
> just goes to show this is a very complicated problem.

One stupid question about the current code:

static inline void ext4_decode_extra_time(struct inode_time *time, __le32 extra)
{                               
       if (sizeof(time->tv_sec) > 4)
               time->tv_sec |= (__u64)(le32_to_cpu(extra) & EXT4_EPOCH_MASK)
                               << 32;
       time->tv_nsec = (le32_to_cpu(extra) & EXT4_NSEC_MASK) >> EXT4_EPOCH_BITS;
}       

#define EXT4_EINODE_GET_XTIME(xtime, einode, raw_inode)                        \
do {                                                                           \
        if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime))                      \
                (einode)->xtime.tv_sec =                                       \
                        (signed)le32_to_cpu((raw_inode)->xtime);               \
        else                                                                   \
                (einode)->xtime.tv_sec = 0;                                    \
        if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime ## _extra))            \
                ext4_decode_extra_time(&(einode)->xtime,                       \
                                       raw_inode->xtime ## _extra);            \
        else                                                                   \
                (einode)->xtime.tv_nsec = 0;                                   \
} while (0)

For a time between 2038 and 2106, this looks like xtime.tv_sec is
negative when ext4_decode_extra_time gets called, so the '|=' operator
doesn't actually do anything. Shouldn't that be '+='?

	Arnd

  parent reply	other threads:[~2014-06-02 12:52 UTC|newest]

Thread overview: 124+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-30 20:01 [RFC 00/32] making inode time stamps y2038 ready Arnd Bergmann
2014-05-30 20:01 ` [RFC 01/32] fs: introduce new 'struct inode_time' Arnd Bergmann
2014-05-31  7:56   ` Geert Uytterhoeven
2014-05-31  8:39     ` Andreas Schwab
2014-05-31 13:19       ` Geert Uytterhoeven
2014-05-31 13:46         ` Andreas Schwab
2014-05-31 14:54       ` Arnd Bergmann
2014-05-31 16:15         ` Geert Uytterhoeven
2014-05-31  9:03   ` H. Peter Anvin
2014-05-31 14:53     ` Arnd Bergmann
2014-05-31 14:55       ` H. Peter Anvin
2014-05-30 20:01 ` [RFC 02/32] uapi: add struct __kernel_timespec{32,64} Arnd Bergmann
2014-05-30 20:18   ` H. Peter Anvin
2014-05-31 15:09     ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 03/32] fs: introduce sys_utimens64at Arnd Bergmann
2014-05-31  9:22   ` Andreas Schwab
2014-05-31 14:55     ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 04/32] fs: introduce sys_newfstat64/sys_newfstatat64 Arnd Bergmann
2014-05-30 20:01 ` [RFC 05/32] arch: hook up new stat and utimes syscalls Arnd Bergmann
2014-05-30 20:01 ` [RFC 06/32] isofs: fix timestamps beyond 2027 Arnd Bergmann
2014-05-31  7:59   ` Geert Uytterhoeven
2014-05-31  8:47     ` H. Peter Anvin
2014-05-30 20:01 ` [RFC 07/32] fs/nfs: convert to struct inode_time Arnd Bergmann
2014-05-30 20:01 ` [RFC 08/32] fs/ceph: convert to 'struct inode_time' Arnd Bergmann
2014-05-30 20:01 ` [RFC 09/32] fs/pstore: convert to struct inode_time Arnd Bergmann
2014-05-30 21:14   ` Kees Cook
2014-05-30 20:01 ` [RFC 10/32] fs/coda: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 11/32] xfs: " Arnd Bergmann
2014-05-31  0:37   ` Dave Chinner
2014-05-31  0:41     ` H. Peter Anvin
2014-05-31  1:14       ` Dave Chinner
2014-05-31  1:22         ` H. Peter Anvin
2014-05-31  5:54           ` Dave Chinner
2014-05-31  8:41             ` H. Peter Anvin
2014-05-31 15:46               ` Nicolas Pitre
2014-06-01 19:56                 ` Arnd Bergmann
2014-06-01 20:26                   ` H. Peter Anvin
2014-06-02 11:02                     ` Arnd Bergmann
2014-06-02  1:36                   ` Nicolas Pitre
2014-06-02  2:22                     ` Dave Chinner
2014-06-02  7:09                       ` Geert Uytterhoeven
2014-06-02 10:56                     ` Arnd Bergmann
2014-06-02 11:57                       ` Theodore Ts'o
2014-06-02 12:38                         ` Arnd Bergmann
2014-06-02 13:15                           ` Theodore Ts'o
2014-06-02 12:52                         ` Arnd Bergmann [this message]
2014-06-02 13:07                           ` Theodore Ts'o
2014-06-02 15:01                             ` Arnd Bergmann
2014-06-02 14:52                         ` H. Peter Anvin
2014-06-02 15:04                       ` Chuck Lever
2014-06-02 15:31                         ` Theodore Ts'o
2014-06-02 17:12                           ` H. Peter Anvin
2014-06-02 18:50                             ` Arnd Bergmann
2014-06-02 22:29                             ` Theodore Ts'o
2014-06-02 22:32                               ` H. Peter Anvin
2014-06-02 23:32                                 ` Theodore Ts'o
2014-06-02 23:33                                   ` H. Peter Anvin
2014-06-03 13:09                                   ` Roger Willcocks
2014-06-02 18:52                         ` Arnd Bergmann
2014-06-02 18:58                         ` Roger Willcocks
2014-06-02 19:04                           ` Chuck Lever
2014-06-02 19:10                             ` Arnd Bergmann
2014-06-01  0:39               ` Dave Chinner
2014-06-02 14:00             ` Joseph S. Myers
2014-05-31 15:37         ` Arnd Bergmann
2014-06-01  0:24           ` Dave Chinner
2014-06-02  0:28             ` Dave Chinner
2014-06-02 11:35               ` Roger Willcocks
2014-06-02 11:43               ` Arnd Bergmann
2014-06-03  0:32                 ` Dave Chinner
2014-06-03  7:33                   ` Arnd Bergmann
2014-06-03  8:41                     ` Dave Chinner
2014-06-03  9:16                       ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 12/32] btrfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 13/32] ext3: " Arnd Bergmann
2014-05-31  9:10   ` H. Peter Anvin
2014-05-31 14:32     ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 14/32] ext4: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 15/32] cifs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 16/32] ntfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 17/32] ubifs: " Arnd Bergmann
2014-06-02  7:54   ` Artem Bityutskiy
2014-05-30 20:01 ` [RFC 18/32] ocfs2: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 19/32] fs/fat: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 20/32] afs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 21/32] udf: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 22/32] fs: convert simple fs to inode_time Arnd Bergmann
2014-05-30 23:06   ` Greg Kroah-Hartman
2014-05-30 20:01 ` [RFC 23/32] logfs: convert to struct inode_time Arnd Bergmann
2014-05-30 20:01 ` [RFC 24/32] hfs, hfsplus: " Arnd Bergmann
2014-05-31 14:23   ` Vyacheslav Dubeyko
2014-05-30 20:01 ` [RFC 25/32] gfs2: " Arnd Bergmann
2014-06-02  9:52   ` Steven Whitehouse
2014-05-30 20:01 ` [RFC 26/32] reiserfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 27/32] jffs2: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 28/32] adfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 29/32] f2fs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 30/32] fuse: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 31/32] scsi: fnic: use current_kernel_time() for timestamp Arnd Bergmann
2014-05-30 20:01 ` [RFC 32/32] fs: use new inode_time definition unconditionally Arnd Bergmann
2014-05-31 14:30 ` [RFC 00/32] making inode time stamps y2038 ready Vyacheslav Dubeyko
2014-06-03 12:21   ` Arnd Bergmann
2014-05-31 14:51 ` Richard Cochran
2014-05-31 15:23   ` Arnd Bergmann
2014-05-31 18:22     ` Richard Cochran
2014-05-31 19:34       ` H. Peter Anvin
2014-06-01  4:46         ` Richard Cochran
2014-06-01  4:44     ` Richard Cochran
2014-06-02 13:52 ` Joseph S. Myers
2014-06-02 19:19   ` Arnd Bergmann
2014-06-02 19:26     ` H. Peter Anvin
2014-06-02 19:55       ` Arnd Bergmann
2014-06-02 21:57         ` H. Peter Anvin
2014-06-03 14:22           ` Arnd Bergmann
2014-06-03 14:33             ` Joseph S. Myers
2014-06-03 14:37               ` Arnd Bergmann
2014-06-03 21:38             ` Dave Chinner
2014-06-04 15:03               ` Arnd Bergmann
2014-06-04 17:30                 ` Nicolas Pitre
2014-06-04 19:24                   ` Arnd Bergmann
2014-06-05  0:10                     ` H. Peter Anvin
2014-06-10  9:54                       ` Arnd Bergmann
2014-06-02 21:02     ` Joseph S. Myers
2014-06-04 15:05       ` Arnd Bergmann

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